As a result of their increased performance in terms of output and specific power and power density, synchronous machines with permanent magnets now have an extensive application in the field of motor vehicles.
These electrical machines can be produced with a wide range of powers and speeds, and have applications both in vehicles of the “all-electric” type and in vehicles with low CO2 emission of the type known as “mild hybrid” and “full hybrid”.
Mild-hybrid applications generally concern electrical machines of approximately 8 to 15 kW, for example an electric motor which is fitted on the front face of a thermal engine, and is coupled to it by a drive belt. With an electric motor of this type, it is possible to reduce the capacity of the thermal motorisation (engine downsizing) by providing electric torque assistance which supplies additional power, in particular during restarting. In addition, fraction at low speed, for example in an urban environment, can also be ensured by this same electric motor.
Another example of application of electrical machines in this power range is the driving of a centrifugal compressor of a system for double supercharging of a thermal engine. At low speed the electric compressor assists the turbo-compressor which is driven by the exhaust gases, and makes it possible to dispense with an additional step in the reduction of the capacities.
Applications of the full-hybrid type generally concern motors of 30 to 50 kW, for architectures of a series and/or parallel type, with the level of integration which is more refined than that of the electric motor(s) in the traction chain of the vehicle.
However, the batteries of these electric vehicles are sensitive to climatic conditions, and the autonomy of the vehicle can be greatly reduced in the most stringent conditions. An air-conditioning system is therefore necessary.
In vehicles with a thermal engine, the compressor of the air-conditioning system is generally coupled mechanically to this engine.
In electric vehicles, the compressor is driven by an electric motor which must comply with numerous constraints, not only in terms of power, torque and speed of rotation, but also dimensions and weight.
A motor of this type is discussed in an article which was submitted in the conference “Progress in Electromagnetism Research Symposium” in 2011 in Marrakesh, Morocco, by M. Kanchoul et al (“Design and study of a permanent magnet synchronous motor”, p. 160, PIERS, 20-23 Mar. 2011).
This concerns a synchronous motor with permanent magnets of the NdFeB type, with nominal power of 6 kW, maximum torque of 6 Nm, and a maximum speed of 10,000 rpm. The weight of the motor is less than 2 kg, and its length is less than 50 mm.
In these circumstances, in order to comply with ever-increasing energy constraints, the inventive body has determined a need for a motor with increased performance.